There is the issue of "my cousin's friend said X" and then there is the issue of the police officer/military guy not knowing their X from a hole in the ground.

I had a bud (real story, I was there) who went to a guy from the SF group on post to put a scope on his hunting rifle. He couldn't figure out why he couldn't get it sighted in. The SF guy had mounted it sideways. Just because someone is SF, Ranger, DELTA, Boy Scouts, or a SEAL doesn't mean they are a weapons expert. Yes, some are the finest in the world, but not all. There are also medics, commo, intel, log, engineer, and many other fields in that world.

We had a young man with us on my last deployment who NEVER left the laundry room for his 15mn tour. I tried many times to get him out of the wire with my patrol, however, he fought to not go. He is a combat vet now. I would not advice someone to take weapons training from him.

Same for police. Many don't like weapons and rarely shoot.

You have to be an educated consumer of info. If it sounds too good to be true (or like crap) odds are it is.

A police or military member who is into weapons and has been there/done that may be a great trainer. However, that does not make all of them so.